J. N. Am. Benthol. Soc., 1994, 13(4):569-579 @ 1994 by The North American Benthologkal Society Phylogenetics and the classification of the Timpanoga complex (Ephemeroptera:Ephemerellidae) W. P. MCCAFFERTY AND T-Q. WANG Department of Entomology, Purdue University, West Lafayette, Indiana 47907 USA Abstract. The Timpanoga complex is a holophyletic group of mayflies in the subfamily Ephem­ erellinae consisting of 21, mostly North American species, distinguished by the absence of lamellate gills on abdominal segment 3 in the larvae, and associated absence of the gill socket remnants in subimagos and adults. A phylogenetic reclassification is proposed, based on a cladistic analysis, and is an example of reclassification necessary in much of the Ephemeroptera. Of the options available for generic classification, the one proposed is both informative in terms of expressing diversity within the complex and practical in terms of allowing morphological differentiation in all life stages, including both sexes of alate stages. Three main sequential lineages are recognized as the genera Attenella, Eurylophella, and Timpanoga [=Dannella n. syn.]. The two main phylogenetic branches in Eurylophella are treated as subgenera Dentatella and Eurylophella s.s. The two main phylogenetic branches of Timpanoga are treated as subgenera Dannella and Timpanoga s.s. A key to known stages of genera and subgenera incorporates newly discovered characteristics of gill socket and postero­ lateral projection remnants in adults and subimagos, and polar cap characteristics of eggs. A clado­ gram of the four species of Attenella indicates that A. soquele and A. attenuata are sister species commonly derived with a sister branch represented by A. margarita, and that these three species represent a sister group of A. delantala. Key words: Timpanoga complex, Ephemerellidae, cladistics, phylogenetic reclassification, Attenella, Eurylophella, Timpanoga. The mayfly group, or taxon, we refer to as the higher taxa within the family Ephemerellidae Timpanoga complex includes species that have (see Hubbard 1990) have not been phylogenet­ been classified in the genus Ephemerella Walsh ic, but instead have had only a roughly defined, (subgenera Timpanoga Needham, Eurylophella phenetic basis. For this reason recognition of Tiensuu, Attenella Edmunds [originally as At- the Timpanoga complex as a subtribe or any oth­ tenuatella], and Dannella Edmunds), or more re- er hierarchical category remains tenuous until cently in the genera Timpanoga, Eurylophella, At- phylogenetic studies of the pannote mayflies tenella, and Dannella. Revisions of Timpanoga are completed. Such phylogenetic revisions of (Allen and Edmunds 1959), Eurylophella (Allen Ephemeroptera are in keeping with the philos­ and Edmunds 1963), Attenella (Allen and Ed- ophy and techniques elaborated by McCafferty munds 1961), andDannella (Allen and Edmunds (1991). 1962) provided species-level interpretations that Edmunds (1959) divided the genus Ephemer­ have remained remarkably stable. Currently, 21 ella into several subgenera, including those of species (19 North American, 2 European) are the Timpanoga complex cited above. McCafferty placed in this complex. Furthermore, only two (1977) showed that each of these Timpanoga new species belonging to this group have been complex subgenera was monophyletic and also described (Allen 1977, McCafferty 1977), and deduced their phylogenetic relationships cla­ only two names have fallen to synonymy (Ber- distically based on several larval and adult char­ ner 1984), since the revisionary studies of Allen acters. Allen (1977) described a new species, and Edmunds. Ephemerella bartoni, in the Timpanoga complex McCafferty (1977) showed that the Timpanoga and placed it in the subgenus Dannella. Mc­ complex was a monophyletic group defined by Cafferty (1978) showed that E. bartoni, despite the unique synapomorphic loss of the gill pair some superficial resemblance to Dannella based on abdominal segment 3 (larvae having lamel- on symplesiomorphies, had none of the apo­ late gills only on segments 4-7). Allen (1984) morphies found in the lineage leading to Dan­ recognized this taxon as the subtribe Timpano- nella, but instead had apomorphies common to gae of the tribe Ephemerellini (Ephemerellidae: the opposite lineage leading to the Eurylophella. Ephemerellinae). Divisions and rankings of Allen (1980) raised the Timpanoga complex sub- 569 570 W. P. MCCAFFERTY AND T-Q. WANG [Volume 13 genera to the rank of genus, and they have gen­ life stages of all higher taxa of the Timpanoga erally been recognized as such since that time. complex, incorporating some newly discovered Allen (1980) also redefined Dannella so that it characteristics of adults, subimagos, and eggs. would continue to include bartoni, and he erect­ We also cladistically analyze the interspecific ed the subgenus Dentatella for bartoni. Allen's relationships of Attenella for the first time. revised concept of Dannella, however, is appar­ ently polyphyletic as will be shown below. Methods Historically, generic classifications of Ephem­ eroptera have been proposed on the basis of Eighteen of the 19 nominal North American little or no phylogenetic information and have species of the Timpanoga complex were exam­ often incorporated certain "gap" criteria, as ined for comparative morphological characters proposed, for example, by Edmunds (1962). (see details in Material examined section, be­ McCafferty (1991) thoroughly discussed this low). In the few cases where known stages of method and its inherent limitations in express­ species were not available to us, we relied on ing phylogenetic relationships. The increase in published descriptions. Voucher specimens are nominal genera of already known taxa of in the Purdue Entomological Research Collec­ Ephemerellidae (Allen 1980) has been paral­ tion, West Lafayette, Indiana. leled somewhat in Baetidae (e.g., Waltz and Standard cladistic methods (including the de­ McCafferty 1987) and Heptageniidae (e.g., termination of character polarity by the out­ Flowers 1980). Other recent treatments of Bae­ group method, the inference of common an­ tidae (Novikova and Kluge 1987) and Hepta­ cestry by common possession of derived geniidae (Kluge 1988) have resulted in extreme character states, and the resolution of possible lumping of genera. We mention this because conflicting data by parsimony) are essentially such disparities among classificatory interpre­ after Hennig (1966), Ross (1974), and Wiley tations are often a concern to the users of tax­ (1981). Because of relatively low numbers of onomy, and thus they require prompt and prac­ operational taxonomic units (OTUs) analyzed tical resolution. Arguments over splitting or and characters used, no computer-aided ana­ lumping of genera, however, are moot if phy­ lytical programs were necessary for generating logeny has not been detailed. In the case of branching sequences. Outgroups are explained Ephemerellinae, we intend to offer at least a under the phylogeny sections, below. partial resolution of the classification issue here. In the case of Baetidae and Heptageniidae, phy­ Material examined logenetic data remain inconclusive; however, it appears that splitting into groups to express the The following is a short-form accounting of monophyletic nature of those groups is provi­ the species (listed alphabetically), life stages (a sionally preferable to lumping of such groups = adult, e = egg, 1 = larva), and geographic solely because they apparently lack character regions (abbreviated) represented by the ma­ "gaps" in one of their life stages. terial we were able to examine for this study. The relatively straightforward phylogeny of Note that generic classification of species are the Timpanoga complex provides the necessary after the revision proposed here. More detailed basis, and thus an excellent opportunity, for information regarding this material is available formulating a phylogenetic generic classifica­ from us upon request. A. attenuata: l, a, e, AR, tion. The main purpose of this study therefore, GA, MA, PA, VA; A. delantala: l, CA; A. marga­ is to re-evaluate the present superspecific clas­ rita: l, ID; A. soquele: l, CA; Ephemerella maculata: sification of the species of the Timpanoga com­ a, e, CA; Eurylophella aestiva: l, AR, IN; E. bartoni: plex in light of this phylogeny and to revise l, ON; E. bicolor: l, a, e, GA, IN, ME, NC, ON, the classification as necessary. The cladogram SC, TN; E. coxalis: l, IN, NC; E. funeralis: l, a, e, is to a large extent deduced from characters that AR, GA, IN, MA, MD; E. lodi: l, WA; E. lutulenta: have been discussed previously by McCafferty l, GA, ON, Ml, NC, TN; E. prudentalis: l, a, e, (1977, 1978) but not presented in strict cladistic ME, MA, NC, NS, PQ, SC; E. temporalis: l, a, e, fashion as here. In addition, we provide a first GA, IN, KY, ME, NC, NH, VT; E. verisimilis: l, a, stage-associated diagnostic key to the known e, MA, ME, NS, SC; T. hecuba: l, a, AZ, BC, MT; 1994) SYSTEMATICS OF THE TIMPANOGA COMPLEX 571 T. Zita: 1, a, e, IN, NC, WI; T. provonshai: 1, AR; jections are distinct on adult segments 4-7 on T. simplex: I, a, e, IN, MA, Ml, NB, VA, WI. some species (Figs. 6, 8); they are poorly de­ Numerous outgroup genera and species rep­ veloped on other species (Fig. 10), being barely resentatives were also studied in general but discernible on segments 6 and 7. are not elaborated here. Smith (1935) was the first to describe eggs of any species of the Timpanoga complex (consid­ Diagnosis